Impact line printers use an endless type-band which is impacted by print hammers arranged in a row. The band is commonly made of metal such as steel on which a row of raised characters and timing marks have been formed on one side. The drive system for revolving the metal band commonly comprises a pair of pulleys one of which is the drive pulley and the other an idler pulley. The band is trained around the pulleys in tension with the reverse side of the band in contact with the pulley to be driven by friction. It is customary to provide a long platen of metal or other hard material behind the band in the areas between the pulleys as a backup to the band. The flat surface of the platen engages the band at all times. The continuous sliding contact of the type band on the platen punctuated by the frequent impacts of the hammer causes the band and platen to wear to the point where one or both must be replaced. Various wear prevention means have been provided to reduce or eliminate the wear. Among these is a wear prevention layer or strip bonded to the face of the platen. Usually the material is one that has low friction properties and is resistant to deformation by impact. One such material used on printers such as the IBM 6262 Printer is a polymer. In such printers it is customary to operate the band drive at speeds of 100-700 inches per second.
In previous impact line printers after a period of time (months or years of operation) motor problems develop. Print quality is reduced and motor overheating may occur resulting in termination of printer operation.
The following publications describe increased friction due to polishing:
1. THE FRICTION AND LUBRICATION OF SOLIDS, Bowden, F. P., Tabor, D., Oxford University Press, 1971, p. 98. PA0 2. "The Influence of Surface Roughness on Wear", Bayer, R. G., Sirico, J. L., WEAR 35 (1975) 251-260. PA0 3. "Effect of Counterface Roughness on the Friction and Wear of Polyethylene Under a Sliding condition Involving Surface Melting", Tanaka, K., Yamada, Y., WEAR OF MATERIALS 1987, The International Conference on Wear of Materials, Houston, Tex., Edited by Ludema, K. C., University of Michigan, Lib. of Congress No. 77 7229. PA0 4. "Tribology of Polymers", Santner, E., Czichos, H., Tribology International, April, 1989, Vol. 22 No. 2, p. 103 to 109.
According to English abstracts Japanese unexamined application Kokai 56-67261 to Fijutsu LTD describes a platen with grooves to reduce the contact area but not in the area opposing the hammers. Japanese unexamined application Kokai 56-67262 to Fijutsu Ltd. describes a groove in a platen opposing to the lower end surface of the type belt to reduce dirt between the belt and platen. U.S. Pat. Nos. 1,200,779 and 2,756,861 show cylindrical platens for typewriters with grooves. U.S. Pat. Nos. 4,510,862 by Alt et al assigned to IBM Corporation and 4,211,166 to Hardt discuss reducing friction between the belt and platen.